Foundry core and dry binder for the preparation thereof



Patented Dec. 14, 1937 PATENT OFFICE Fomsmw coma AND nay Bmnnaron THE- 1 1 PREPARATION THEREOF [Fred H. LaheJHillsdale, N. Y., assignor to Her- 1 les Powder Company, Wilmington, Del., 11

corporation" of Delaware N6, rawin Application August 12, .1936, 1 1 Serial No. 95,706 .1 v

1 "l his linvention[relates to foundry cores and dry binders for thepreparation thereof.

1Heretoiore, in makingfoundry, cores for use. in

the productionof castings, it has been the practice1to mix coresand withone-of a -.variety,of

,dry or liquid binders, epg. pulverized foundry pitch, pulverized rosin, pulverized cereal, pulverized casein, sulfite, pulp waste liquor, molasses,

sour beer, linseed,1soya bean,,or other vegetable oil, oil-rosin mixtures,- known ascore oils, etc.

"Themixture of sand and binder is then moistened.

with suiiicient water, so that item be rammed or blown into core boxes of various shapes and sizes, corresponding to the shapes and sizes of cavities it is desired to produce by means of the coresn 1 1 When the core box is removed; the grains of sand must be bound together by the binder, so

its disadvantages.

as topermit handling in an approved manner and transferring to .an oven. inthe oven the cores are then baked to expel the water, drive off volatile constituents, and make the corecapable of withstanding ferrostatic pressure encountered in the casting operation. 1

Incasting, the heat of the molten metal burns l 1 out the binder, 1 the gases from which vent through the cores and molds, leaving the core in a friable form or as loosely held sand, readily removable from the cavity in the casting when cooled. 1

Each of the above mentioned core binders has Foundry pitch has no "green strength" and is also hard to clean from the cavity. Pulverized rosin reverts to solid rosin on storage, 1. e. flows together to form a solid mass.

Rosin-kerosene-linseed oil mixtures (coreoils) tend to crystallize and precipitate the rosin on storage. Cereal binders produce cores which swell, absorb moisture, and give rise to large volumes of acrid smoke in the casting operation. Liquid core binders migrate to the surface of the core and form a hard, impenetrable skin. Linseed oil binder must dry by oxidation, which slows down production. Casein, skimmed milk, etc., are hydro'scopic and putrescible when used in cores.

resin overcomes the above difliculties encountered in the uselof oldart core binders. l

The gasoline-insoluble, pinewood resinI em- 1 ploy in the preparation 'of my improved core,

binder and cores ;madetherefrom is hereby de- 5 1 fined as the resin such as may be produced from resinous wood, described and claimed in application,Serial No. 61,745, filed January 31 l936,-by Lucius C. Hall, which resin maybe produced by extracting resinous wood with acoal tar hydrocarbon, removing said hydrocarbon by evaporation, leavinga residue comprising a mixture of wood rosin and the new resin, extracting wood rosin from saidresidue by a petroleum hydroe carbon, leaving thenew, gasoline-insoluble, pine wood resin, p

' It will be noted thatthe unextracted soybean 1 meal used in my improved core binder, contains appreciable, but variable, quantities of soya bean oil which latter enters into the composition.

I have found that pulverized, gasoline-insoluble pine wood resin, as described above, possesses poor green strength when used as a core binder. However, this poor green strength is overcome by the admixture with thetoughening unextracted soybean meal or flour. I have also found that while cores made with linseed oil, soybean oil, or other vegetable oils, require longbaking at high temperatures, soybean meal or flour, which contains usually about 17% of oil, when mixed with the gasoline-insoluble pine wood resin above described, causes a reaction during the baking, in which the oil and the resin form a condensate, resulting in the production in a short baking period of a high-strength, superior core. 1

In preparing my improved foundry core composition I mix intimately, for example by grinding together, unextracted soya bean meal and the gasoline-insoluble pine wood resin, hereinbefore described. For example, equal parts thereof may be ground together, and cores made therewith by mixing such composition with foundry sand in a ratio of, for example, 55 parts by weight of sand to 1 part by weight of the composition, and baking the core for about 1.5 hours at about 425 F. The green strength of such cores is satisfactory before baking, and after baking the core has a tensile strength of 177 pounds per square inch. Furthermore, such baked cores may, as a test, be stored in a moisture-saturated atmosphere overnight, and found, after such storage, to have a tensile strength of about 165 poundsper square inch, i. e., a loss of less than 7%. Storage in a moisture-saturated atmosphere causes a severe loss in strength of cores produced by methods heretofore employed.

Furthermore, I have found that my improved core compositions are practically non-putrescent, due to the presence therein of my special resin, hereinbeiore described, which resin contains certain, complex polyphenols, which act as a preservative A further advantage of my improved core compositions is that they are dry, and easy to use, as compared to the fluid or semifiuid compositions heretofore used.

It will be appreciated that other proportions of ingredients may be used by me in preparing my improved core composition, depending upon the size, type, or complexity of the core it is desired to produce. Nor do I limit myself to the sand/binder ratio or temperature or time or baking, given above by way of example.

It will also be appreciated that I may add additional soybean oil to my core binder composition, or I may use extracted soybean meal and soybean oil, in place of unextracted soybean meal, thus reproducing, in effect, unextracted soybean meal. I may also employ extracted soybean meal and other vegetable oils, such as linseed oil, in place of unextracted soybean meal, and still obtain the advantages, due to the presence oi. the gasoline-insoluble pine wood resin, of superior strength of core and hardening by condensation eifects.

What I claim and desire to protect by Letters Patent is:

1. As a core binder, a mixture of soybean meal containing a vegetable oil, and a gasoline-insoluble, pine wood resin produced by extracting resinous wood with "a coal tar hydrocarbon, removing said hydrocarbon by evaporation, extracting the residue with a petroleum hydrocarbon, and recovering a gasoline-insoluble resin.

2. As a core binder, a mixture of soybean meal, a vegetable oil, and a gasoline-insoluble, pine wood resin produced by extracting resinous wood with a coal tar hydrocarbon, removing said hydrocarbon by evaporation, extracting the residue with a petroleum hydrocarbon, and recovering a gasoline-insoluble resin.

3. As a core binder, a mixture of unextracted soybean meal and a gasoline-insoluble, pine wood resin produced by extracting resinous wood with a coal tar hydrocarbon, removing said hydrocarbon by evaporation, extracting the residue with a petroleum hydrocarbon, and recovering a gasoline-insoluble resin.

4. As a core binder, a mixture of equal parts of unextracted soybean meal and a gasolineinsoluble, pine wood resin intimately mixed together, said pine wood resin being produced by extracting resinous wood with a coal tar hydrocarbon, removing said hydrocarbon by evaporation, extracting the residue with a petroleum hydrocarbon, and recovering a gasoline-insoluble resin.

5. A green foundry core consisting of core sand, unextracted soybean meal and a gasolineinsoluble, pine wood resin produced by extracting resinous wood with a coal tar hydrocarbon, removing said hydrocarbon by evaporation, extracting the residue with a petroleum hydrocarbon, and recovering a gasoline-insoluble resin.

FRED H. LANE. 

